Various scrambling techniques have been devised to print sensitive information and images onto a medium so that they cannot be read by unauthorized individuals. A separate decoding device is provided which, when laid over the printed image, renders the scrambled information or image legible. These scrambling techniques have been proposed for use in applications where security is needed and ready access to the encoded material must be available. For example, to facilitate banking transactions it has been proposed to encode the signatures of depositors into bank passbooks. The bank, which possesses a decoder for the scrambled signature, can readily verify the authenticity of a signature when funds are withdrawn. It has similarly been proposed to encode signatures to the back of credit cards for quick and easy verification of the identity of the person using the card.
Scrambling techniques are also used for promotional purposes. Because the techniques require a participant in the promotion to decode a hidden image, such techniques often are entertaining. It also has been proposed to employ scrambling techniques in games of chance, such as lottery cards, that are sold at the retail level. The techniques are suitable for such application, because a consumer would not know whether the game piece he or she has purchased is a winner until the game piece has been decoded.
A particular technique for scrambling information or images involves suppressing from view some of the area of an image printed in a figure. The image is typically suppressed from view in an ordered manner, such as along a series of parallel stripes. For convenience, the series of parallel stripes, or other ordered manner in which the image is suppressed, will be referred to herein as a "base image." Because the image often can still be discerned even though part of it has been suppressed, extraneous and meaningless imagery is printed to the figure where the image has been suppressed, and also in the background of the image, at about the same coloration and density as the portion of the printed image that has not been suppressed. The extraneous and meaningless imagery thereby confuses and scrambles the remaining image, rendering it unintelligible.
A mask may be created from the base image. When the mask is laid over the scrambled image it obscures the extraneous imagery and leaves the unsuppressed parts of the image exposed to view, so that one is able to decode the scrambled image. This technique for encoding images can take many forms, several of which are described in U.S. Pat. No. 2,952,080 to Avakian et al., U.S. Pat. No. 3,621,589 to Jones et al., U.S. Pat. No. 3,279,095 to Carlson, and U.S. Pat. No. 3,227,474 to Hoeflinger. For simplicity, the disclosure of each of the foregoing patents is hereby incorporated by reference as if fully set forth herein.
The technique disclosed in these patents can be practiced either manually or electronically. The technique can be practiced manually, for example, by physically erasing portions of an image and physically printing the meaningless background information to the figure. The technique can also be practiced by photographic or other means whereby images are superimposed onto one another to create the scrambled image. The technique further can be practiced electronically by programmed manipulation, suppression, and superimposition of digitized images of the meaningful scrambled image and the meaningless background imagery.
Ordered base images that comprise an organized and uniform arrangement of opaque and transparent units often are employed in existing scrambling techniques. Ordered configurations typically are employed so that a person can more readily register a decoder with a scrambled image to unscramble the image. While ordered base image configurations make decoding scrambled images easier, they also render the scrambled image less secure against unauthorized decoding. As a base pattern becomes more ordered, the risk that an unauthorized person can discern a scrambled image without using the decoder increases. Security is further compromised by the fact that in many instances only one or a few base images are used to scramble a tremendous number of images, because of the difficulty of maintaining and using more than just a few decoding mechanisms. If someone were to decipher only one scrambled image without a decoder, then the person may be able to decode multiple scrambled images hidden with the same base image.